This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A366538 #10 Apr 26 2025 21:35:13
%S A366538 1,2,2,2,2,4,2,2,4,2,4,2,4,4,2,2,4,2,4,4,4,2,2,4,4,2,8,2,4,4,4,4,2,4,
%T A366538 4,2,8,2,4,4,4,2,4,2,4,4,4,2,4,4,4,2,8,2,4,4,4,8,2,4,4,8,2,2,4,4,4,4,
%U A366538 8,2,4,2,4,2,8,4,4,4,2,8,4,4,4,4,4,2,4
%N A366538 The number of unitary divisors of the exponentially 2^n-numbers (A138302).
%C A366538 Also, the number of infinitary divisors of the terms of A138302, since A138302 is also the sequence of numbers whose sets of unitary divisors (A077610) and infinitary divisors (A077609) coincide.
%H A366538 Amiram Eldar, <a href="/A366538/b366538.txt">Table of n, a(n) for n = 1..10000</a>
%F A366538 a(n) = A034444(A138302(n)).
%F A366538 a(n) = A037445(A138302(n)).
%t A366538 f[n_] := Module[{e = FactorInteger[n][[;;, 2]]}, If[AllTrue[e, # == 2^IntegerExponent[#, 2] &], 2^Length[e], Nothing]]; f[1] = 1; Array[f, 150]
%o A366538 (PARI) lista(max) = for(k = 1, max, my(e = factor(k)[, 2], is = 1); for(i = 1, #e, if(e[i] >> valuation(e[i], 2) > 1, is = 0; break)); if(is, print1(2^#e, ", ")));
%Y A366538 Cf. A034444, A037445, A077609, A077610, A138302, A366539.
%Y A366538 Similar sequences: A366534, A366536.
%K A366538 nonn,easy
%O A366538 1,2
%A A366538 _Amiram Eldar_, Oct 12 2023